The present invention relates to drilling tools for boring holes into the earth and, in particular, to a drilling tool especially suited for the oil well drilling industry and for boring deep wells for use in generation of electrical power by converting water pumped through the well into steam so as to run a generator.
Because of the substantial cost of drilling wells, the drilling industry is constantly attempting to improve the efficiency of drilling bits, since even a minor improvement in the efficiency of a bit can result in substantial savings in the overall drilling of a well.
Drill bits utilizing rotating cones having outwardly projecting serrated teeth, discrete carbide lugs or the like have been utilized for many years in the drilling industry. Applicant of the present application has developed drill bits of this type over the years and is the holder of many United States patents for such drill bits.
However, through extended study, applicant has found that the drill bits of the prior art having spaced teeth, lugs or the like have certain inherent inefficiencies. For example, it has been found that drill bits having cones with teeth projecting therefrom typically require approximately at least three and often as many as eight rotations of the bit for the teeth to completely create a single substantially continuous groove or cut into an imaginary circumferential layer such that the first layer is broke away and the teeth can start working on the second layer.
A more serious problem is that the teeth tend to be aligned on the various cones such that a following set of teeth tend to drag in the track of a predecessor set of teeth. That is, the bit tends to suffer from the same inefficiency realized when a vehicle with a set of tires tries to follow in the muddy tracks of a predecessor vehicle and finds that it spends much of its time and energy spinning rather than digging in and obtaining traction.
Consequently, applicant determined that, in order to improve the efficiency of a drill bit of this type, it was necessary to provide a bit having a continuous, uninterrupted cut such that, with each revolution, the exposed surface of the ground would receive a complete circumferential cut. In addition, applicant determined that it was necessary to have the cutting edges of one set of cones offset from the cutting edges of a second set of cones so as to avoid having a trailing set of cutting edges slide in the tracks of predecessor cutting edges.
In designing such a drill bit, applicant also discovered a synergistic effect between his cutting edges such that one set of cutting edges has a tendency to dig into the surface and the other set of cutting edges has a tendency to shatter the rock or soil between the first set of cutting edges substantially reducing the pressure required on the bit and also substantially reducing the work required to rotate the bit since significantly fewer rotations are required to make a bore of a given depth, thereby producing an extremely efficient bit.